February is the second month of the year in the Julian and Gregorian calendars. The month has 28 days in common years or 29 in leap years, with the 29th day being called the leap day. It is the first of five months to have fewer than 31 days (the other four being April, June, September, and November) and the only one to have fewer than 30 days. Seven months (January, March, May, July, August, October, and December) have 31 days, leaving the four previously mentioned months (April, June, September, and November) to have exactly 30 days. This means the other eleven months have at least 30 days. Thus, February is the third and last month of meteorological winter in the Northern Hemisphere. In the Southern Hemisphere, February is the third and last month of meteorological summer (the seasonal equivalent of August in the Northern Hemisphere).
A month is a unit of time used with calendars, which is approximately as long as a natural period related to the motion of the Moon; month and Moon are cognates. The traditional concept arose with the cycle of moon phases; such months (lunations) are synodic months and last approximately 29.53 days. Researchers have deduced that people counted days in relation to the Moon's phases from excavated tally sticks as early as the Paleolithic age.